(Problem) Raspberry Pi OpenCL - bus access error

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Offline Micha1982

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« on: April 11, 2018, 03:44:41 AM »
Hi,
I know that this is a bit crazy and everything is in alpha-state (also the driver) but regarding that Netrender hopefully work with OpenCL in future I am trying to get OpenCL running on my Raspberry Pi with Mandelbulber  :embarrass:

Just for testing purposes and to see how fast it is compared to its cpu...

I already have managed to get everything being recognized in Mandelbulber to activate it in the menu, but when I press render, the program crash immediately and terminal says "bus access error"...

Can someone tell me why exactly maybe? Is this error driver-related or is there something missing in Mandelbulber related to Videocore?
Many thanks already for a short explanation.

 
« Last Edit: April 11, 2018, 04:04:42 AM by Micha1982 »

Offline buddhi

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« Reply #1 on: April 11, 2018, 06:40:24 AM »
It's interesting trial.
It could be just not enough RAM memory to compile OpenCL kernels.
How much RAM is in this Raspberry?

Offline Micha1982

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« Reply #2 on: April 11, 2018, 07:15:56 AM »
Its a Pi 3 with 1gb and actually set 192mb to the gpu. Same result If I reduce it to 64 for the gpu.

And I am trying it with this, this and this driver by Doe300 after I found this thread.
« Last Edit: April 11, 2018, 07:56:56 AM by Micha1982 »

Offline Micha1982

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« Reply #3 on: April 11, 2018, 07:55:00 AM »
(doublepost sorry)

Offline Micha1982

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« Reply #4 on: April 16, 2018, 10:31:10 AM »
How much memory does it need to compile at all? However I set the memory-split, I get the same message/crash all the time. Any other ideas what could cause this maybe? Already tried to look into the logfile, but even with log-verbosity 2 there is nothing inside it.

Surely the Raspberry is not fast...but maybe useful later in Netrender or something like that anyway as it does not need much power, is cheap and could run 24/7...

Offline buddhi

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« Reply #5 on: April 17, 2018, 08:21:10 PM »
I have checked memory usage. I got folowing numbers about RAM usage:
- nVidia OpenCL compiler: between 100-1200MB (depending how many effects are enabled and how complex hybrid fractal is rendered)
- mandelbulber - about 250MB
Usage of GPU mem: about 50MB when SSAO and DOF are disabled.

So the problem could be not in amount of needed memory but in not complete implementation of OpenCL in gfx drivers for Raspberry PI. There is even written in description of the driver that:
Quote
Of course it is far from complete, but it runs about 50% of the OpenCL CTS test-cases for supported features, 60% of the test-programs of a slightly modified boost compute library, 71% of the test cases for EasyCL, as well as some other test-programs.
Similar problems you can have if you try to use open source driver for AMD or Intel. With drivers for Intel gfx chips you can render basic fractals only in "fast" mode. In other case the program crashes because of gfx driver.


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